KR100911058B1 - Method of finding metadata server - Google Patents

Abstract

The present invention relates to a metadata server search method for searching a Ubiquitous Sensor Network (USN) metadata server in a distributed environment.

The present invention is characterized in that for storing the location information of the metadata server using a location server cluster in a distributed environment, and when the client metadata search request, the location of the metadata server in which the metadata of a specific resource is stored .

Thus, the present invention can provide a simple and consistent interface to the client using the metadata server in terms of the metadata server, and also increase the transparency of service development and reduce the overall cost and maintenance cost required for the development. .

USN, Sensor, Sensor Network, Metadata, Directory, Location Server, End-to-End, Hierarchy

Description

How to Retrieve Metadata Servers {METHOD OF FINDING METADATA SERVER}

The present invention relates to a metadata server search method, and more particularly, to a metadata server search method for searching a Ubiquitous Sensor Network (USN) metadata server in a distributed environment.

The present invention is derived from the research conducted as part of the IT growth engine technology development project of the Ministry of Information and Communication and the Ministry of Information and Communication Research and Development (Task Management Number: 2006-S-022-02, Task name: USN middleware platform technology development).

USN stands for 'Ubiquitous Sensor Network', which provides sensing functions, computing functions, and network functions to all objects such as human living spaces, living devices, and machines. By providing a network, it refers to a network that allows to enhance the convenience and safety of human life. The USN enables automation in various fields, and through this technology, it is possible to provide various services convenient to humans such as telematics, home network, inventory management, patient management, animal management, natural disaster management, and ITS system.

The sensor network for realizing a ubiquitous environment refers to a network mainly composed of wireless sensor nodes and equipped with a communication function. Such sensor networks generally have densely distributed sensor nodes to compensate for failures in sensing and data delivery, and transmit data based on broadcast communications. It is also a feature of sensor networks to have limited power, memory, and computing power using wireless, small sensor nodes.

When building a system using a sensor network, it is difficult to understand and use all the underlying technologies. Therefore, USN middleware and sensor node middleware have been developed to make it easier to build a system based on a sensor network.

At this time, USN middleware is responsible for filtering, integrating, and analyzing sensing data collected from heterogeneous sensor networks to extract, store, manage, and search for meaningful context information, and transfer it to application services or to link and integrate services.

Sensor node middleware exists between various sensor application softwares, operating systems and network functions, and supports various requirements for maintenance, installation / deployment, and application execution.It is installed on sensor nodes and sink nodes to update and apply the sensor network program. Perform the function of programming adjustment according to the change. In addition, the sensor node middleware is responsible for the database, data storage management, and data management and processing function data fusion functions suitable for various applications.

In general, when constructing a USN-based system, the system includes a system for managing metadata of a sensor network in the system. Information about what kind of sensor network is connected to the system, sensor network location, function, connection method, operation method, sensor node included in sensor network, sensing type of each sensor node, sensing data, By establishing a metadata management system that manages information about the location of sensors, middleware or application programs can utilize information about sensor networks.

Such a metadata management system may be configured as a separate system or simply exist in the form of a database so that related systems can access and register, inquire and modify necessary metadata.

However, metadata management in these systems is all done in one system, making it suitable for use with a small number of sensors in a small area. In the future, many sensors will be installed in a large area, so that metadata of sensor networks cannot be managed and provided in heterogeneous wide area / distributed sensor network environments.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and provides a method for searching a USN metadata server in a distributed environment.

In the present invention, when there are a plurality of systems for managing metadata of a sensor and a sensor network in a wide-area distributed environment in which many sensors exist, metadata management for managing metadata of a corresponding sensor to retrieve metadata of a specific sensor It aims to retrieve the server's location.

In order to solve this problem, according to the present invention, in order to use a sensor in a system using a sensor or a sensor network, information about a sensor and a sensor network including the sensor is required, so that many sensors are widely spread and multiple meta Implement a method of finding a metadata management server that manages metadata of specific sensor network resources in a wide area and distributed environment where the data management server manages metadata for each sensor network.

According to an aspect of the present invention, there is provided a method for searching a metadata server in a distributed environment, the method comprising: storing location information of a metadata server using a location server cluster, and upon requesting a metadata search of a client, a specific resource It provides a metadata server search method comprising the step of searching for the location of the metadata server is stored metadata.

Here, the location information refers to a pair of ID of a resource described by the metadata and connection information of a metadata management server in which the metadata is stored. The location server cluster also uses one or a plurality of metadata location servers.

The metadata server search method comprises a metadata location server group, which is a set of servers capable of providing an address of a metadata server managing the metadata by organically exchanging information between the metadata location servers. It further comprises the step of operating.

In this case, configuring and operating the metadata location server group may be performed by configuring the metadata location server group using a hierarchical structure. Alternatively, the configuring and operating the metadata location server group may be performed by configuring the metadata location server group using an end-to-end structure. Alternatively, the configuring and operating the metadata location server group may be performed by configuring the metadata location server group by combining a hierarchical structure and an end-to-end structure.

The metadata server search method may include: receiving, by the metadata location server, a metadata server search request from the metadata server, checking whether a resource ID received from the metadata server is stored locally, and If the resource ID exists locally, returning location information of the corresponding metadata server to the metadata server.

In addition, and the metadata server search method, if the resource ID does not exist locally, it transmits the resource ID to the other metadata location server of the metadata location server group and requests the search of the corresponding metadata server It further comprises the step.

According to another aspect of the present invention, in a method for searching a metadata server in a distributed environment, when the client's request to search and provide metadata, confirming whether to manage the metadata corresponding to the request, the metadata If the data is not being managed, using the location server to retrieve location information of the metadata server managing the metadata, and accessing the metadata server using the retrieved location information to perform the request. It provides a metadata server search method comprising the step of transmitting to the client after receiving the response.

In the metadata server search method, a local location server in a hierarchy of metadata location servers receives an ID of a resource together with a metadata server search request through the metadata server. Determining whether the ID belongs to its own area, and if the resource ID does not belong to its own area, the local location server designates its parent location server as a next location registration server; Transmitting the resource ID to the next location registration server together with a metadata server search request, determining whether the next location registration server receives the resource ID from the local location server and belongs to its own area; If the received resource ID belongs to its own area, the next location registration server Determining whether the server is an end location registration server that stores an ID-IP pair; and, if the end location registration server is configured, converting an IP address of a metadata server managing metadata for the resource ID to the local location server. The method further includes returning to.

In addition, if the metadata server search method is not the end location registration server, finding a location registration server of a lower layer corresponding to the resource ID and returning the IP address of the child location server to the local location server. And the local location server further comprises the step of sending the IP address to the next location registration server, and transmitting the resource ID with the metadata server search request to the next location registration server.

Alternatively, the metadata server searching method may include checking whether the local location server itself is responsible for the resource ID in the end-to-end structure of the metadata location server group. Transmitting the resource ID with the metadata server search request to the next location server, and the next location server receives the resource ID and checks whether the received resource ID is in charge of the next location server. If not, the next location server finds a value corresponding to an area in which the resource ID exists in its finger table, and the next location server sets the IP of the node corresponding to the found value. Returning the address to the local location server, the local location server receives the IP address and A further comprises the step of transmitting with the resource ID and meta data server search request to the next location server, the next location server, and to.

In addition, the metadata server search method further includes the step of returning its own IP address to the local location server if the next location server itself is responsible for the received resource ID.

The metadata server search method may further include: when a new location server is added to the location server group, the new location server obtains information about one location server existing in the location server group, and the new location server obtains the obtained location server. Requesting the location server to search for the metadata server in charge of the area containing the ID, and the obtained location server confirms whether it is responsible for the ID, and the obtained location server itself If the ID is not in charge, the obtained location server finds a value corresponding to the area where the ID exists in its finger table, and the obtained location server uses the IP address of the node corresponding to the found value as the new location. Returning to the server, the new location server receives the IP address and stores it as the next location And transmitting the ID to the next location server together with the metadata server search request, wherein the next location server receives the ID and checks whether the received ID is in charge of the received location server. If the next location server itself is responsible, the next location server returns its IP address to the new location server, the new location server requests the next location server to divide the area, and the next location server Dividing its area in half, handing one side to the new location server and in charge of the other, the next location server provides all of its finger table information to the new location server, and its previous node pointer Modifying the new location server to the new location server; Requesting to change the next node pointer of this node to the new location server by connecting to the previous node pointer of the new location server, the new location server making its previous node pointer the previous node pointer of the next location server, and the next node pointer. Making the next location server, and the new location server further includes modifying its own finger table based on the finger table information.

Here, the metadata server search method further includes periodically finding a node of an entry of its finger table and modifying the finger table. The metadata server search method may further include modifying the finger table by finding a node of an entry of its own finger table when the average node visit count is a predetermined value or more during the search. In addition, the metadata server search method further includes the step of modifying its finger table based on the contents by returning the area of responsibility of the location server together with the IP address returned in the middle of each search.

As described above, according to the present invention, it is possible to provide a client using the metadata management server with a simple and consistent interface in terms of metadata server, and also to develop the USN system in a wide sensor network environment in which developers and client programs are distributed. This will increase the transparency of service development and ultimately reduce the overall and maintenance costs of development.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “… module” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software. Can be.

In a system with many sensors and using many sensors, in addition to the sensing values read from the sensors, the system and the sensor network must know the metadata so that the system can read and control the desired information from the desired sensor. In addition, in a wide sensor network and distributed environment in which all metadata cannot be managed by one metadata management server, multiple metadata management servers exist, and metadata corresponding to a specific sensor is stored by a metadata management server. Finding out if it's managed is essential.

Accordingly, in the present invention, when there are a plurality of systems for managing metadata of a sensor and a sensor network in a wide-area distributed environment in which many sensors exist, metadata for managing metadata of a corresponding sensor to retrieve metadata of a specific sensor is present. Implement a way to retrieve the location of the management server. In this case, the present invention is used for sensor network metadata sharing through interworking among a plurality of sensor network metadata management servers.

The present invention receives an ID of a sensor network resource (ie, a sensor network, a sensor node, a sensor, an actuator, a sensing type, etc.) as an input, and finds an address of a metadata management server managing metadata of the corresponding resource. In this case, the present invention proposes three models (ie, centralized, tree, and end-to-end) and uses a combination of the models, and only the terminal nodes have search target values. Accordingly, the present invention can provide metadata, which is not locally managed, for a sensor network of a wide area in a distributed environment as metadata that is locally managed.

In the present invention, when multiple metadata servers exist in a distributed environment and a plurality of location servers having location information of metadata exist, the present invention searches for a metadata server managing specific metadata. In this case, the present invention searches for a server that manages metadata using IDs of resources such as centralized, hierarchical, end-to-end, and combined structures. Accordingly, the present invention makes it appear as if all metadata is managed at the metadata management server when the client uses the metadata management server.

The present invention is to find a directory server which directory server to use. In this case, the present invention searches for a metadata management server when there are several metadata management servers. When metadata of resources of a sensor network are managed by various systems in a distributed environment, the metadata management server is searched for. .

In addition, the present invention configures a distributed directory server using various types of distributed lookup systems. In this case, the present invention searches distributed metadata using various lookup techniques (3 types).

A metadata server search method according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a flowchart illustrating a metadata server search method according to an embodiment of the present invention.

A metadata server search method according to an embodiment of the present invention will be described briefly with reference to FIG. 1 as follows.

In a distributed metadata server search method, a location server cluster may be used to store location information of a USN metadata server and retrieve a location of a USN metadata server where metadata of a specific resource is stored. Here, the location server cluster refers to a case where one or more metadata location servers 103 are used.

That is, when a USN client 101 (that is, a terminal) that requires metadata for a sensor and a sensor network in a distributed environment accesses the metadata management server 102-1 and requests metadata search and provision, the meta Confirm that the data management server 102-1 manages metadata corresponding to the metadata search and provision request of the USN client 101. In this case, when the metadata corresponding to the metadata search and provision request of the USN client 101 is not managed, the metadata management server 102-1 accesses the metadata location server 103 to the terminal 101. Search the location of the metadata management server 102-n that manages metadata corresponding to the metadata search and provision request of the server. Here, the location information means a pair of the ID of the resource described by the metadata and the connection information of the metadata management server 102-n in which the metadata is stored.

Thereafter, the metadata management server 102-1 accesses the metadata management server 102-n received as a search result (that is, address information of the metadata management server 102-n) and connects the USN client 101 to the metadata management server 102-1. Forwards metadata search and provisioning requests The metadata management server 102-1 receives a response corresponding to the metadata search and provision request of the USN client 101, and transmits a response corresponding to the search and provision request to the USN client 101.

Here, the metadata location server 103 configures and operates the metadata location server group in order to manage and search the metadata management servers 102-1 and 102-n managing specific metadata. At this time, in configuring the metadata location server group, the metadata location server group is configured and operated using a hierarchical structure. In the metadata location server group using a hierarchical structure, the metadata location server group is configured and operated using the physical location information of the metadata management servers 102-1 and 102-n.

Alternatively, in configuring the metadata location server group, the metadata location server group is configured and operated using an end-to-end structure.

Alternatively, in configuring the metadata location server group, the metadata location server group is configured and operated by combining a hierarchical structure and an end-to-end structure.

Furthermore, in configuring the metadata location server group, the metadata location server group is configured and operated by combining a centralized structure, a hierarchical structure, and an end-to-end structure. That is, when using a plurality of metadata location server 103, the metadata location server group includes both a hierarchical structure, an end-to-end structure, or a combination of two or more structures.

Referring to the metadata server search method according to an embodiment of the present invention again as follows.

A client 101 requesting USN metadata connects to a specific metadata management server 102-1 and requests metadata. If the metadata management server 102-1 does not directly manage metadata corresponding to the metadata search and provision request of the USN client 101, the metadata management server 102-1 manages the metadata using the metadata location server 103. It receives the address of the metadata management server 102-n.

The metadata management server 102-1 uses the address information to connect to the metadata management server 102-n and replace the metadata request received from the USN client 101 with the result of the request. Forward to 101.

Accordingly, the USN client 101 determines which metadata management server 102-1, 102-n the metadata required is, how to find the metadata management server 102-1, 102-n, In addition, it is unnecessary to perform tasks such as requesting the same metadata again from the other metadata management servers 102-1 and 102-n.

Accordingly, the present invention provides a simple and consistent interface to the USN client 101 using the metadata management server 102-1, 102-n in terms of the metadata management server 102-1, 102-n. Can be. In addition, the present invention makes it possible for the metadata management servers 102-1 and 102-n to which the USN client 101 connects to manage all of the metadata of countless sensors and sensor networks, thereby making it possible for developers and client programs. It facilitates the development of USN system in this distributed wide area sensor network environment. As a result, it is possible to increase the transparency of service development and reduce the overall cost and maintenance cost required for development.

Metadata retrieval system using the USN metadata server retrieval system to which the present invention is applied, as shown in Figure 1, USN client 101, a plurality of metadata management server (102-1, 102-n), meta Data location server 103. In addition, the metadata retrieval system according to an embodiment of the present invention further includes an internal system (not shown in the drawings for convenience of description) of the USN system that requires USN metadata.

The USN client 101 may be a USN middleware or a USN application. The USN client 101 may request metadata management servers 102-1 and 102-n to retrieve metadata about a corresponding resource using an ID of a sensor network resource. The metadata is provided from the metadata management servers 102-1 and 102-n.

The metadata management servers 102-1 and 102-n manage metadata for specific sensors and sensor networks, and receive corresponding metadata search and provision requests from the USN client 101 to provide corresponding metadata. Here, the metadata management servers 102-1 and 102-n are metadata management servers that manage metadata of a wide area sensor network in a distributed environment. Since only metadata of a specific sensor network is managed, multiple metadata management servers are provided. exist. Metadata management servers 102-1 and 102-n provide a standardized interface for requesting retrieval and provision of metadata remotely.

The metadata location server 103 manages the ID of a specific sensor network resource and the addresses of metadata management servers 102-1 and 102-n managing the metadata of the resource in pairs, and manages the metadata management server 102. -1, 102-n receives the ID of the sensor network resource as an input and provides the addresses of the metadata management servers 102-1 and 102-n managing the metadata of the corresponding resource. Here, the metadata location server 103 manages IDs of specific sensor network resources and addresses of the metadata management servers 102-1 and 102-n in pairs. In order to manage the metadata management servers 102-1 and 102-n of the wide area sensor network in a distributed environment, there is one or several metadata location servers 103. The metadata location servers 103 are a group of metadata location servers that are a set of servers that can organically exchange information and provide addresses of metadata management servers 102-1 and 102-n for managing specific metadata. Configure

In this case, the metadata location server group may be configured in one of three models, a centralized structure, a hierarchical structure, and an end-to-end structure, or a combination of the three models.

According to the centralized structure, there is one metadata location server 103 and manages IDs of all resources and addresses of metadata management servers 102-1 and 102-n corresponding thereto.

In the hierarchical structure of metadata location servers, there are several metadata location servers 103. Each metadata location server 103 forms a hierarchical relationship based on the ID of the resource to be managed so that the entire metadata location server group forms a tree structure. Here, as a method of constructing a hierarchical structure, the hierarchical structure may be formed by looking at the resource ID itself as a sequential bit and dividing it into bit units. In addition, the hierarchical structure may be configured by using the location information of the metadata management servers 102-1 and 102-n included in the resource ID.

Hereinafter, an operation of a metadata search system using a USN metadata server search system according to an embodiment of the present invention will be described with reference to FIG. 1.

First, the USN client 101 requests the first metadata management server 102-1 to retrieve metadata about a corresponding resource using the ID of the sensor network resource.

Accordingly, the first metadata management server 102-1 receives a metadata search request from the USN client 101, retrieves locally managed metadata, and searches for metadata corresponding to the metadata search request of the USN client 101. Check for the presence of data. At this time, if metadata exists, the first metadata management server 102-1 provides the metadata to the USN client 101 as a result of the search.

On the other hand, if there is no metadata corresponding to the metadata search request of the USN client 101 locally of the first metadata management server 102-1, the first metadata management server 102-1 is a sensor. The metadata location server 103 is requested to find the metadata management servers 102-2 to 102-n managing the metadata of the corresponding resource using the ID of the network resource.

Accordingly, the metadata location server 103 receives the metadata management server search request from the first metadata management server 102-1, and the resource ID received from the first metadata management server 102-1 is locally located. Check if it is saved. In this case, if the resource ID exists locally, the metadata location server 103 returns the corresponding metadata server address to the first metadata management server 102-1.

However, if the resource ID does not exist locally, the metadata location server 103 passes the resource ID to another metadata location server (not shown in the drawing for convenience of description) corresponding to the group of metadata location servers. Request the search of the metadata management servers 102-2 to 102-n.

At this time, the resource ID is repeatedly transmitted to other metadata location servers in order to find the metadata management servers 102-2 to 102-n corresponding to the resource ID in the metadata location server group. Accordingly, when a request arrives to the metadata location server managing the resource ID and the corresponding addresses of the metadata management servers 102-2 to 102-n, for example, the nth metadata management server 102-n ) Is returned to the first metadata management server 102-1 which initially requested the metadata location server 103 via the metadata location server in the reverse order of the requested order.

Then, the first metadata management server 102-1 receiving the address of the n-th metadata management server 102-n managing the resource ID uses the address to control the n-th metadata management server 102-n. Request a metadata search using the resource ID.

Accordingly, the n-th metadata management server 102-n provides metadata corresponding to the resource ID to the first metadata management server 102-1.

Accordingly, the first metadata management server 102-1 provides the USN client 103 with metadata received from the n-th metadata management server 102-n.

2 is a diagram illustrating a metadata location server group in a hierarchical structure according to an exemplary embodiment of the present invention.

As shown in FIG. 2, the metadata location server group 200 having a hierarchical structure according to an embodiment of the present invention regards an ID as a unique bit string and regards a corresponding bit string. The scope is divided by layers to distribute the load between location servers (LS).

In order to load balance between the location registration servers LS, a k-ary search tree is constructed using the location registration server LS. At this time, the height (Height) and the degree (Degree) of the corresponding search tree structure are determined by the processing capacity and overall load of each location registration server LS.

When viewing the location registration server LS as a node, each node stores its parent node's address. The child node does not need to store the parent node.

Each node stores a prefix of an ID space that is owned by a sub-tree whose child is a child, and the length of the prefix. For example, in the case of an ID space corresponding to '010xxxxxx', '010' and '3' are stored.

Each node stores the prefix of the ID space stored by its child nodes, its length, and its IP address. At this time, the prefix stored by the child node may not be the same length. For example, its prefix is '010xxxx', and there are three child nodes, which may be '0100xxx', '01010xx', or '01011xx'.

The sum of all the prefixes of the child nodes must be equal to their prefixes. That is, no empty space should exist. For example, if its prefix is '010xxxx', and there are two child nodes and the prefix is '0100xxx' and '01011xx', there is an empty space. The leaf node stores the actual ID-IP pair corresponding to the ID space that it stores instead of the child node.

The configuration of the metadata location server group 200 in a hierarchical structure first determines the number of location registration servers LS, and configures the location registration server LS based on the tree configuration method described above by the location server administrator.

Here, each metadata management server defines one end location registration server as its own local location server in the metadata location server group 200.

Each location registration server does not have to be run on a separate device, but a single location server may store information that will be stored by multiple location registration servers. For example, all three location registration servers in the left sub-tree of FIG. 2 may be aggregated and stored in one location registration server.

The operation of the metadata location server group 200 in a hierarchical structure is performed in the same manner as the DNS lookup. First, when the metadata management server receives a user's request for retrieving metadata using the resource ID, the metadata management server connects to its local location server and informs the local location server of the resource ID.

Accordingly, the metadata management server performs a repetitive search based on the local location server. That is, the local location server first determines whether the ID belongs to its own area, and returns the IP to the metadata management server if the ID belongs to its own area.

On the other hand, if the ID does not belong to its own area, it designates its parent location server as the next location registration server. The ID is also sent to the next location registration server.

Accordingly, the next location registration server, which has received the ID from the local location server, determines whether the requested ID belongs to the ID area in charge thereof. At this time, if the requested ID does not belong to the ID area in charge of its own, the IP of its own parent location server is returned to the local location server. Here, the corresponding IP becomes the next location registration server.

If the ID belongs to its own area, it is determined whether it is an end point registration server storing the ID-IP pair, and if it is an end point registration server storing the ID-IP pair, Return the IP corresponding to the ID, that is, the IP of the metadata management server that manages metadata about the resource of the ID, to the local location server.

The local location server then completes the process of finding the metadata management server by returning it to the first requested metadata management server.

On the other hand, if the ID belongs to its own area and is not an end location registration server, the location registration server of the lower layer corresponding to the ID is found and the IP of the child location server is returned to the local location server. Here, the corresponding IP becomes the next location registration server. Then, as described above, the ID is repeated after the ID is transmitted to the next position registration server.

3 is a diagram illustrating an example of a metadata location server group having a hierarchical structure using location information of a metadata management server according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the metadata location server group 300 that forms a hierarchical structure using location information of the metadata management server according to an embodiment of the present invention is configured as a metadata management server. By configuring using the geographical location of the user, it is possible to optimize the response time for the request of the message.

First, the entire area is assumed to be a 'rectangle' and divided into quarters. Again, divide each area into four equal parts. Repeat this until you have a hierarchy of the desired height.

3 is an example of dividing into an area having a height of '3'. The area where the metadata management server exists for each area is displayed. With one location server in each zone, the server in charge of the upper zone becomes the parent node of the four servers in charge of the lower zone. Servers corresponding to the end nodes store the actual ID-IP pairs.

3 shows a hierarchical structure between these location servers. In fact, the location server does not need to exist for the area where the metadata management server does not exist.

The nice thing about doing this is that information about geographically close nodes is stored on the same end node, so that information about the associated sensor network or sensor node can be obtained faster. Forming such a structure increases the number of location servers required. In fact, if a location server is executed in each metadata management server, there is no real burden.

In the metadata location server group 300 having a hierarchical structure using location information of each metadata management server, each node has the following information.

Each metadata management server stores its own location information. As in the case of the sensor network, it is represented by 42 bits. It is divided into 21 bits of longitude and 21 bits of latitude. With the combination of each first bit of longitude and latitude, the whole area is divided into four areas. That is, '0-0-', '0-1-', '1-0-' and '1-1-'.

Each region is divided into four regions again, and this process is repeated. Each node stores the address of its parent node. Child nodes do not need to store parent nodes.

Each node stores an area in which a sub-tree whose child is a child is in charge. Each node stores the area that its child nodes are in charge of and their IP addresses.

The sum of all areas of the child node must be equal to its area. Child zones that do not have a metadata management server need not have a location server. The end node stores the actual ID-IP pair corresponding to the ID area it stores instead of the child node.

The searching of the metadata management server in the metadata location server group 300 having a hierarchical structure using location information of the metadata management server may be performed by dividing the ID into bits without using the location information. This is the same as the search operation in the metadata location server group that configures.

4 is a diagram illustrating a metadata location server group constituting an end-to-end structure according to an exemplary embodiment of the present invention.

As shown in FIG. 4, the metadata location server group 400 constituting the end-to-end structure according to an embodiment of the present invention allows each metadata management server to simultaneously perform the role of the location server LS.

Of course, the location server LS is executed one by one on the machine where the metadata management server is executed. Various P2P systems have been proposed, but since most of the performances such as the number of messages until query processing are similar, in the present invention, a P2P structure is formed based on a chord system, which is the most representative P2P system. In a code system, the ID works the same for both storing and not storing metadata management server information.

In the end-to-end structure of the metadata location server group 400, the information stored in each node is as follows.

Each location server LS has its own unique ID. It is easily set to the ID of one sensor network that this metadata management server is in charge of. The ID can be regarded as one point in the distance by the Modulo Operation. By this definition, each location server LS corresponds to a point on the circle.

It has its own ID interval. On this circle we store which area the node is responsible for. Basically, it contains its own ID and takes care of the area after the ID of the node just before it.

It has an ID-IP pair, and stores an ID-IP pair belonging to its own ID area. It also stores the IP address and ID of the next node that is its next node pointer (succ).

Finally, it stores the IP address and ID of the node just before it, which is the previous node pointer (pred).

With the foregoing, once all nodes have a circular topology based on the next and previous node pointers. Given the ID of the sensor network resource, it can go to the location server (LS) that stores the ID-IP pair based on the next node pointer and the previous node pointer.

However, in this case, there is a possibility that all nodes (ie, location servers) should be visited in the worst case. Since this is not desired by the present invention, in order to speed up the retrieval, a finger table for managing pointer information of the location server LS in a table form is further stored.

The finger table is configured as follows. If the total number of nodes is n and one node has its ID 'x', this node stores a pointer to the following node.

First, because the ID is fixed at 128, it has 128 pointers. The nodes included in this pointer are: IP address and ID of the node having an area containing ID 'x + 1', and IP address and ID of the node having an area containing ID 'x + 2' and area containing ID 'x + 4' The IP address and ID of a node that has an area, including the ID 'x + 2 ^k '. At this time, the k value is from '0' to '127'.

The searching method in the metadata location server group 400 having an end-to-end structure is a process of searching for a location server in charge of a specific ID starting from one local location server.

First, check whether the local location server itself is responsible for this ID, and if it is in charge of this ID, the search ends.

But if you're not in charge of the ID, you'll call yourself Next Location Server.

Then, the ID is sent to the next location server to request a search. Therefore, the next location server checks whether this ID belongs to the area in charge of itself, and if the ID belongs to the area in charge of it, returns its IP to the local location server and the search is terminated.

On the other hand, if the next location server does not take care of the ID, it finds a 'k' value corresponding to the area where the corresponding ID exists in its finger table. That is, find the value of 'k' whose ID belongs to (x + 2k-1, x + 2k). Returns the IP address of the node corresponding to the found 'k' value to the local location server.

Accordingly, the local location server uses the IP received from the next location server as the next location server, and transmits an ID to the next location server to repeat the operation of requesting a search.

On the other hand, when a new node is added in the metadata location server group 400 that constitutes the end-to-end structure, all information to be stored by this node must be newly configured. You also need to modify the information that some other nodes have. The operation is as follows.

The new location server 'N' obtains information about one location server 'E' existing in the existing P2P location server group 400 from an administrator.

The new location server 'N' sends its ID to the location server 'E' and requests to find the node in charge of the area containing this ID.

Accordingly, the location server 'E' is a location server 'T in charge of an area including the ID of the new location server' N 'through a search process in the metadata location server group 400 having the end-to-end structure as described above. Finds its IP and returns it to the new location server 'N'.

In other words, the location server 'E' checks whether it is responsible for the ID received from the new location server 'N'. At this time, if the location server 'E' itself is not responsible for the ID of the new location server 'N', the 'k' value corresponding to the area where the ID of the new location server 'N' exists in its finger table is found. The location server 'E' returns the IP address of the location server 'T' corresponding to the found 'k' value to the new location server 'N'.

Accordingly, the new location server 'N' uses the IP address received from the location server 'E' as the next location server, and transmits its ID to the next location server (that is, location server 'T') to request a search. Accordingly, the location server 'T' checks whether it is in charge of the ID received from the new location server 'N', and returns its IP address to the new location server 'N' if it is in charge of the received ID. .

Accordingly, the new location server 'N' requests the location server 'T' to divide the area.

Then, the location server 'T' divides its own area in half, transfers the front area to the new location server 'N', and takes care of its back half. At this time, the location server 'T' provides all of its finger table information to the new location server 'N'. In addition, the location server 'T' modifies its old node pointer to the new location server 'N'.

The new location server 'N' accesses the previous node pointer of the location server 'T' and requests that the next node pointer of this node be changed to the new location server 'N'. Also, the new location server 'N' sets its previous node pointer to the previous node pointer of the location server 'T' and the next node pointer to the location server 'T'.

The new location server 'N' modifies its own finger table based on the finger table information provided from the location server 'T'. For this modification, the search operation of the searching process in the metadata location server group 400 having the end-to-end structure as described above for each 'k' is repeated. In practice, it is not necessary to perform the search operation on all 'k's.

In addition, if only the previous node pointer and the next node pointer are actually stored correctly, the information of the finger table is slightly different, but there is no problem in the search. However, stabilization is carried out for accurate information.

There are three ways of stabilization. First, periodically find and modify a new node of an entry of its finger table. Second, instead of periodically, it may be performed when the average number of node visits is greater than or equal to a certain value. Third, the user's finger table is modified based on this information by returning the location server's area of responsibility along with the IP address returned in the middle of each search.

Hereinafter, referring to FIG. 5, the configuration of the metadata location server group configured by combining the end-to-end structure and the hierarchical structure will be described.

5 is a diagram illustrating a metadata location server group configured by combining an end-to-end structure and a hierarchical structure according to an exemplary embodiment of the present invention.

As shown in FIG. 5, the metadata location server group 500 configured by combining an end-to-end structure and a hierarchical structure according to an embodiment of the present invention includes all metadata management servers in various groups 510 and 520. Divide.

The metadata management servers in each group 510 and 520 are formed in one hierarchical structure. Child nodes of the hierarchy are gathered to form an end-to-end structure. The child node simultaneously plays the role of a child in the hierarchy and the role of a node in the end-to-end structure.

The search operation of the metadata location server group 500 configured by combining the end-to-end structure and the hierarchical structure is performed in the same manner as the search process of the hierarchical structure first. If the pattern is not matched in the child nodes, the end-to-end structure is used. To search in a different hierarchy.

As described above, when a plurality of systems for managing metadata of a sensor and a sensor network exist in a distributed environment, a location of a metadata management server that manages metadata of a corresponding sensor to retrieve metadata of a specific sensor is present. It was described how to search.

At this time, according to an embodiment of the present invention, a client (ie, a terminal) requesting USN metadata accesses a specific metadata management server to request metadata, and the metadata management server does not directly manage the metadata. In this case, the metadata location server receives the address of the metadata management server managing the metadata, accesses the metadata management server using the address information, and requests the metadata received from the client instead. Have the result delivered to the client. The client thus manages metadata by eliminating the need to manage which metadata server the metadata it needs, how to find the metadata server, and to request the same metadata from another metadata server again. You can provide clients using the server with a simple and consistent interface in terms of metadata servers. In addition, the metadata management server to which the client connects appears to manage all of the metadata of a large number of sensors and sensor networks, thereby facilitating the development of USN systems in a distributed wide-area sensor network environment. do. This can ultimately increase the transparency of service development and reduce the overall cost of maintenance and maintenance.

In addition, the embodiment of the present invention is not implemented only through the above-described apparatus and / or method, but a program for realizing a function corresponding to the configuration of the embodiment of the present invention, and a recording medium (CD-ROM, RAM) on which the program is recorded. , ROM, floppy disk, hard disk, magneto-optical disk, etc.), such implementations can be easily implemented by those skilled in the art to which the present invention pertains from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a flowchart illustrating a metadata server search method according to an embodiment of the present invention.

2 is a diagram illustrating a metadata location server group in a hierarchical structure according to an exemplary embodiment of the present invention.

3 is a diagram illustrating an example of a metadata location server group in a hierarchical structure according to an exemplary embodiment of the present invention.

4 is a diagram illustrating a metadata location server group constituting an end-to-end structure according to an exemplary embodiment of the present invention.

5 is a diagram illustrating a metadata location server group configured by combining an end-to-end structure and a hierarchical structure according to an exemplary embodiment of the present invention.

Claims (18)

In a method for searching a metadata server in a distributed environment in which a plurality of metadata servers are distributed, Receiving a metadata search request including an ID of a resource to be found from the client; Requesting a metadata server search while providing an ID of a resource provided from the client to a location server cluster, wherein the location server cluster includes location information of metadata servers--the location information is connection information of a corresponding metadata server and the Managing the metadata contained in the metadata server includes an ID of a resource described by the metadata server; And Receiving location information of a metadata server including metadata associated with an ID of the resource from the location server cluster; Metadata server search method comprising a. delete The method of claim 1, The location server cluster, A metadata server search method that uses one or more metadata location servers. The method of claim 3, And configuring and operating a metadata location server group, which is a set of servers capable of providing an address of a metadata server managing the metadata by organically exchanging information between the metadata location servers. Server discovery method. The method of claim 4, wherein Configuring and operating the metadata location server group, A metadata server search method for configuring and operating the metadata location server group using a hierarchical structure. The method of claim 4, wherein Configuring and operating the metadata location server group, A metadata server retrieval method for configuring and operating the metadata location server group using an end-to-end structure. The method of claim 4, wherein Configuring and operating the metadata location server group, A metadata server retrieval method comprising combining the hierarchical structure and the end-to-end structure to configure the metadata location server group. The method of claim 4, wherein Receiving, by the metadata location server, a second metadata server search request from a first metadata server, Confirming whether the resource ID received from the first metadata server is stored locally; and Returning location information of a corresponding second metadata server to the first metadata server if the resource ID exists locally; Metadata server search method further comprising. The method of claim 8, If the resource ID does not exist locally, the metadata location server further includes requesting a search for a corresponding metadata server while delivering the resource ID to other metadata location servers in a group of metadata location servers. How to search metadata server. In a method for searching a metadata server in a distributed environment in which a plurality of metadata servers are distributed, Receiving a metadata search request including an ID of a resource to be searched for from a client and confirming whether the metadata corresponding to the request is managed; If the metadata is not managed, the server requests a metadata server search while providing an ID of a resource provided from the client to a location server, and the location server requests location information of metadata servers--the location information corresponds to the location server. Managing access information of a metadata server and an ID of a resource described by metadata included in the metadata server; Receiving location information of a metadata server including metadata associated with an ID of the resource from the location server; Transmitting the request of the client by accessing the corresponding metadata server using the provided location information; And Receiving a response to the request from the metadata server and transmitting the response to the client Metadata server search method comprising a. The method of claim 10, Receiving, by a local location server included in a group of metadata location servers in a hierarchical structure, an ID of a resource together with a metadata server search request requested by the client from a first metadata server; Determining, by the local location server, whether the resource ID belongs to its own area; If the resource ID does not belong to its own area, the local location server designates its parent location server as a next location registration server; The local location server transmitting the resource ID with a metadata server search request to the next location registration server; Receiving, by the next location registration server, the resource ID from the local location server and determining whether it belongs to its own area; If the received resource ID belongs to its own area, the next location registration server determines whether it is an end location registration server storing an ID-IP pair; Returning, to the local location server, an IP address of a second metadata server managing metadata for the resource ID, if the endpoint location registration server; The local location server forwarding the IP address of the second metadata server to the first metadata server Metadata server search method further comprising. The method of claim 11, If it is not the end location registration server, finding a location registration server of a lower layer corresponding to the resource ID and returning the IP address of its child location server to the local location server; and The local location server using the IP address as a next location registration server, and transmitting the resource ID together with the metadata server search request to the next location registration server; Metadata server search method further comprising. The method of claim 10, Checking whether the local location server itself is responsible for the resource ID in the end-to-end structure of metadata location servers, If the resource ID is not in charge, making the local location server itself as a next location server, and transmitting the resource ID with a metadata server search request to the next location server; Receiving, by the next location server, the resource ID and confirming whether the corresponding received resource ID is in charge of it; If not in charge of the received resource ID, the next location server finding a value corresponding to an area where the resource ID exists in its finger table, The next location server returns the IP address of the node corresponding to the found value to the local location server; Receiving, by the local location server, the IP address as a next location server, and transmitting the resource ID with the metadata server search request to the next location server. Metadata server search method further comprising. The method of claim 13, If the next location server itself is responsible for the received resource ID, the next location server further comprises the step of returning its own IP address to the local location server. The method of claim 13, When a new location server is added in the location server group, the new location server obtains information about one location server existing in the location server group, Sending a new location server to the obtained location server and requesting a search for a metadata server in charge of an area including the ID; Confirming whether the obtained location server is responsible for the ID; If the obtained location server itself is not responsible for the ID, the obtained location server finds a value corresponding to an area where the ID exists in its finger table, The obtained location server returns the IP address of the node corresponding to the found value to the new location server; Receiving, by the new location server, the IP address as a next location server, and transmitting the ID along with a metadata server search request to the next location server; The next location server receives the ID and checks whether the received ID is in charge of it; If the next location server itself is responsible for the received ID, the next location server returns its IP address to the new location server, The new location server requesting the next location server to divide a region; The next location server divides its area in half, transfers one side to the new location server, and takes charge of the other; The next location server provides all of its finger table information to the new location server and modifies its previous node pointer to the new location server; The new location server accessing a previous node pointer of the next location server and requesting to change the next node pointer of this node to the new location server, The new location server making its previous node pointer the previous node pointer of the next location server, and the next node pointer the next location server, and The new location server modifying its own finger table based on the finger table information Metadata server search method further comprising. The method of claim 15, And periodically finding a node of an entry in its finger table to modify the finger table. The method of claim 15, And searching for a node of an entry of an own finger table and modifying the finger table when the average node visit count is a predetermined value or more during the search. The method of claim 15, And returning the corresponding area of the location server together with the IP address returned in the middle of each search, and modifying his finger table based on the contents.

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